<!DOCTYPE html>
<head>
    <meta charset="UTF-8">
    <title>...</title>
</head>
<body>
<h1>欢迎登陆</h1>
<form action="" method="get">
    用户名:<input type="text" value="lin" name="username" size="20" maxlength="20" required/><br/>
    密&nbsp;码:<input type="text" value="123" name="password" ><br/>
    <input type="submit" value="OK">
</form>
</body>
</html>